The major purpose of the project is to analyze hematopoiesis and MuLV metabolism in cultured Friend virus induced erythroleukemia cells, in order to elucidate the mechanism of virus-induced leukemia. Since the viral envelope glycoproteins have been implicated as possible causal agents in leukemogenesis, a major focus of the project is to understand the metabolism, structure and function of these glycoproteins. Toward this end we are isolating and studying various mutants which are altered or blocked in their synthesis of these virion glycoproteins. In addition, we are trying to identify the gene products encoded by the Friend spleen focus forming virus. One of these gene products, a glycoprotein with an apparent molecular weight of 55000, has been identified and is being preliminarily characterized.